Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming, and ultimately very expensive endeavors. As a result, over the years, a significant amount of added emphasis has been placed on well monitoring and maintenance. Once more, perhaps even more emphasis has been directed at initial well architecture and design. All in all, careful attention to design, monitoring and maintenance may help maximize production and extend well life. Thus, a substantial return on the investment in the completed well may be better ensured.
In the case of well monitoring and logging, mostly minimally-invasive applications may be utilized which provide temperature, pressure and other production related information. By contrast, well design, completion and subsequent maintenance, may involve a host of more direct interventional applications. For example, the removal of debris or tools and equipment may be required or entire downhole regions may closed off from production. In certain instances, high pressure perforating and stimulating of well regions may be called for. In this case, the active intervention may be preceded by the added intervention of closing off and isolating the well regions with mechanisms capable of accommodating such high pressure applications.
Closing off of a well region for a subsequent high pressure application may be achieved by way of one or more mechanical plugs or packers. Such mechanisms may be positioned at downhole locations and serve to seal off a downhole region adjacent thereto. These mechanisms are configured to accommodate the high pressures associated with perforating or stimulating as noted. Thus, they are generally radially expandable in nature through the application of substantial compressive force as described below. In this manner, slips of the radially expandable mechanisms may be driven into engagement with a casing wall of the well so as to ensure its sufficient anchoring. By the same token, the radial responsiveness of elastomeric portions of the mechanisms may help ensure adequate sealing for the high pressure application to be undertaken.
Unfortunately, delivering and setting such mechanical isolation mechanisms often involves the use of an explosive setting tool. That is to say, a mechanical packer may be positioned by conventional line delivery equipment such as wireline or coiled tubing. However, upon reaching the targeted location downhole, an explosive setting tool coupled to the mechanical packer is used to trigger its deployment. More specifically, a slow-burning explosive charge may be used to generate a high pressure gas which acts upon a hydraulic assembly in order to set the packer.
A host of drawbacks are associated with such explosive setting of a mechanical isolation mechanism. For example, the once triggered, the operator is left with little control or even feedback as to the manner of packer setting. Rather, a signal for firing of the explosive is initiated followed by a slow burn and initially large, but dissipating, hydraulic pressure. No practical control over the speed or reliability of the setting is available, nor feedback concerning the effective degree of setting. Once more, since the setting tool involves the use of a consumable explosive, there is no manner by which to pre-test the setting tool in a controlled environment. That is, the explosive charge may be used only a single time.
Further complicating matters is the fact that these most commonly utilized of setting tools are explosively driven. For safety and security reasons, this can lead to significant delays where their transport to the oilfield is required, particularly where international transport is involved. Indeed, even where delays are avoided, inherent hazards to personnel are involved in the transport of such materials.
In an effort to avoid the use of explosive materials for setting mechanically deployable isolation mechanisms, screw-type linear actuators have been developed in recent years. Such tools are electrically driven and may produce a sufficiently large force for mechanical packer or plug setting from an appropriately sized downhole electric motor. Unfortunately, however, these tools may not be particularly efficient in operation and, due to significant power requirements for starting, may be left inoperable should they stall during operations. Thus, as a practical matter, setting of mechanical isolation devices remains primarily driven by the potentially hazardous and inconsistent drive of blind explosive setting tools.